A comparative study of antagonistic activity spectra of lactic acid bacteria isolated from fermented foods.

The present work aimed to assess the general antagonistic activity against opportunistic pathogens and to compare antagonistic action spectra of lactic acid bacteria (LAB) strains, isolated from Ukrainian traditional fermented foods. Overall, 161 profiles of the antagonistic activity spectrum were obtained from 1056 LAB strains. Among them, 114 profiles were genus-specific and 47 spectra of antagonistic activity were found in LAB strains of different genera. Furthermore, 19 LAB strains were active only against Gram-negative indicator strains and 149 LAB strains only against Gram-positive indicator strains. The size of growth inhibition zones of indicator strains by LAB strains of each genus did not correlate with the level of acidification. Zones of growth inhibition of indicator strains appeared after 6-8 h of incubation and in most cases decreased with further incubation, up to absence after 24 h. The difference in the antagonistic activity of 16-h-old and 24-h-old hours LAB cultures also was found. Among LAB tested, 241 strains are the most promising for further practical use, they have antagonistic action towards 10 indicator strains. The cross-streaking method can be used for rapid screening of bacteriocinogenic LAB strains and has advantages over the well-diffusion assay. To the best of our knowledge, this is the first report on a comparative characteristic of spectra of antagonistic activity against opportunistic pathogens of LAB strains belonging to different genera.

[INTERACTION OF LACTOBACILLUS PLANTARUM 337D UKM B-2627 STRAIN CELLS WITH CLAY MINERALS IN VITRO].

OBJECTIVE: To characterize the interaction of Lactobacillus plantaruni 337D UKM B-2627 strain, which has probiotic properties, with kaolinite and montmorillonite. METHODS: The methods of infrared spectroscopy, transmission electron microscopy, the adsorption-structural static volumetric method, microbiological and statistical methods were used. RESULTS: The characteristics of the porous space of clay mineral particles were practically did not change compared with initial samples during the interaction with L. plantarum 337D UKM B-2627 strain cells, pore size distribution had become wider due to the emergence of large diameter pores, reduced surface area, but the adsorption capacity and the layered structure of clay minerals preserved. For the first time the ef- fect of kaolinite and montmorillonite on growth of L. plantaruni 337D strain in vitro was studied. The greatest stimulating effect of clay minerals was observed within two hours of cultivation. The specific growth rate of L. plantaruni 337D strain was in 5.2 times higher when cultured in MRS medium with 4 % of kaolinite and 6 times more - in MRS medium with 1 % montmorillonite versus control. The presence in the medium of kaolinite or montmorillonite slowed the process of reducing pH during growth of the L. plantarum 337D strain, compared with the control. In the presence of montmorillonite pH decreased more slowly than in the presence of kaolinite. The difference between initial pH value of medium with 4 % kaolinite and after two h (ApH) was 10 times less in comparison with the control. At the same time, pH of the medium with 1 % or 4 % montmorillonite began to decrease after 4 hours of cultivation. CONCLUSIONS: Different effect on the growth of L. plantarum 337D strain due to differences of physical and chemical characteristics of kaolinite and montmorillonite used in the study.